Bandwidth and page size

Bandwidth refers to the speed of the connection between the server and the user.  Wider bandwidth means that more data can be transferred in a given time.

Truth

Some of your visitors will have lots of bandwidth (via coaxial cable or optical fibre).  Some will have narrow bandwidth (via a dial-up telephone line).  You can't tell which is which.  The larger a page on your site is, the longer it will take before it reaches the user. 

Consequences

The larger your page is, in bytes, the greater the percentage of users that will be frustrated by how long it takes to appear.  Frustrated users may go away and not return.

Recommendations

Keep each of your pages as small as possible while still conveying the desired information.

Tips

1. Start to worry when your page (including any images it contains) exceeds 50K bytes.  This is the point beyond which it will take about 10 seconds to reach the user (which is the limit of tolerance for many people) on a 56Kb dial-up line.  The further the page size goes beyond this point, the more you should worry.  Before the worry starts to depress you, reduce the page size or split it into multiple pages.
2. If you have JPEG images on the page, use the 'progressive' option when you create them.  This will actually make them a slight bit larger, but will give the user something to look at while the detail in the image downloads.
3. Using your favorite image editor, experiment with compression of your images to reduce their size.  JPEGs can often be compressed 50% without a noticable loss of image quality.
4. Never reduce the displayed size of an image by specifying a smaller height and width in the HTML or CSS.  The browser will still have to download the entire original image (before discarding enough of it to reduce the size).  (See Image size).
5. If you must use Flash or Java applets, give the user both:
   • A way to skip it and move on to your real content.
   • A progress indicator so the user can see how long they will have to wait for the data to complete loading.
6. If you think everyone has a fast connection and all of the preceeding has become irrellevant, you can check your assumption at http://www.websiteoptimization.com/bw/.  Click through to the most current month to see the statistics.

Index

Last revised 19 Oct 2007